class cat():
    def sayWho(self):
        print("我是小猫")
        pass
class dog():
    def sayWho(self):
        print("我是小狗")
        pass
class pig():
    def sayWho(self):
        print("我是小猪")
        pass
class duck():
    def sayWho(self):
        print("我是鸭子")
        pass
class Person():
    def sayWho(self):
        print("我是人类")
        pass

def intruduction(who):
    for i in who:
        i.sayWho()
        pass
list1=[cat(),dog(),pig(),duck(),Person()]
intruduction(list1)